Here is an article where Paul McMahon walks you through the process of Getting your first programming job in Japan. As you can guess he is not Japanese. He is a developer and he lives in Tokyo so it seems like he knows what he is talking about. Speaking about languages, Paul thinks that:
The greater your technical ability, the less Japanese youll need.
and I tend to agree with him - as in any other country, the lower your technical skills are, the lower are your chances that you will be hired if you are a foreigner who doesn't speak the language.